Air Conditioning fan only works on full blast!

I'm a bit stumped here.

Got a Chevrolet Cavalier 1999 and I just started to use the heater the other day to clear things. It works but only on the 3rd setting which is full blast. The first two settings, the fan doesn't come on at all??? Very odd.

Does anyone have any idea's?

I actually have the same problem in a 1995 Ford E250 cargo van I bought..The Air Conditioner and the heat fan only works on the highest setting. Also, I notice there is an excessive draw on the battery charge as well as the running temperature of the vehicle with the fan running. ie the charge indicatorbegins to drop and the temp gauge begins to increase. Could these problems
be related? Any idea how easy/difficult and what the cost is for me to replace the fan resistor block myself? Also, check the fan resistor block. While you're at it, lubricate the fan motor because if it's binding, the added current draw will damage the block again.